Shadertoy + misc + remove autotools

Adds a mode that will render a "shadertoy" shader (read from file) to faces of a cube. It's a bit limited in that it only supports shaders that aren't using samplers. (Supporting samplers would probably require using the shadertoy web api so we can query the sampler types and src data.. which is pretty easy in python, but less so in C)

Also a few misc patches.

Plus removing autotools.. adding new src files seems like a good time to drop legacy build system. We've removed autotools build support from mesa some time back, so I hope by now everyone has figured out how to use meson+ninja.